Variable-flow pumps of the drum piston type



Jan. 29, 1963 G. GARNIER VARIABLE-FLOW PUMPS oF THE DRUM PIsToN 4TYPE vFiled March 5', 195s 5 Sheets-Sheet 1 GEORGES GARNIER ATTORNEYS Jan. 29, 1963 G. GARNIER 3,075,472

VARIABLE-FLOW PUMPS oF THE DRUM PIs'roN TYPE Filed March 5, 1958 3 Sheets-Sheet 2 j? INVENTOR GEOR GES GARNIER Blvd-M ha@ ATTORNEYS Jan. 29, 1963 G. GARNIER 3,075,472

vARIABLE-FLow PUMPS oF THE DRUM PIsToN TYPE Filed March 5, 1958 5 Sheets-Sheet 5 y my 'u jm The object of the present invention is to provide improvements in variable-How pumps of the drum piston type i.e. having pistons sliding in bores provided in a drum, or rotor, pumps in which the stroke of the pistons in the rotor depends on the position of a cam or swashplate tiltable about an axis orthogonal to the axis of the rotor.

One of these improvements concerns the manner of mounting the rotor. It is known that, to obtain correct pump operation, it is essential that the rotor remains applied constantly against the distribution surface, the slightest gap or separation between the rotor and distribution 'surface creating considerable leakage.

It has been discovered that, to satisfy this condition, the rotor must be carried by at least one main bearing disposed in a Well-defined region in the vicinity of the pivot axis of the cam, and that, if other bearings are provided outside said region, these bearings must have greater play than that of the main bearing or bearings.

The region in which the main bearing or bearings are located is determined mathematically by the condition that the resultant of the forces exerted on the rotor, apart for the reaction of the distribution surface be directed toward said distribution surface and fall within the surface of contact of the rotor and the said distribution surface.

In a particular embodiment, the rotor is carried by a shaft which extends therethrough and is rigidly fixed to the housing, the bearing, or bearings, being disposed in the aforementioned region.

This arrangement is advantageous in that the presence of the cam plate, the piston shoes yand the support plate, makes it practically impossible to provide a bearing outside the rotor in the dened region mentioned hereinbefore.

This arrangement also enables the rotor to be driven by a ring gear machined directly on the rotor and meshing wit-h a gear rigid with the driving shadtof the pump, since only the arrangement of a central shaft permits providing a rotor bearing in a plane perpendicular to the rotor axis and containing said ring gear.

In this case, the invention also provides an arrangement whereby the meshing of the rotor ring gear is such that the delivery passageway of the pump is located in the plane of the meshing and on the side of the axis of the rotor opposed to that of said meshing.

According to another improvement to the centering of the pump body or rotor in the housing, there is provided, in addition to a main bearing on the pump body itself, a second bearing carried by the housing and in which is journalled the cylindrical end of a shaft tted in the pump body, for example by a conical portion, and lixed in position by a nut.

Another improvement is in the pivotal mounting of the tiltable cam or swash plate and provides, in addition to the usual pivot pin, abutment means which exerts on the cam an action balancing the thrust exerted on the cam by the pump pistons, this abutment means being in contact with the cam through the medium of a part-cylindrical face, the axis of the cylinder coinciding with the pivot axis of the cam.

in one embodiment, this abutment means is constituted by lxed parts rigid with the housing or machined in one ice piece with the latter. In a modification, this abutment means is constituted by a balancing piston disposed in a bore in the housing and constantly applied against the rear face of the cam by the delivery pressure in a region denn-ed in suit-able manner -for substantially balancing the thrust exerted on the cam by the pump pistons. Owing to this fixed abutment member, or to this balancing piston, the pivot pin merely maintains the cam in position and is subjected to but a small force.

In another improvement, the plate which applies the piston shoes against Ithe forward face of the cam is positively driven in rotation by the rotor so as notably to reduce friction. This drive could be obtained, on the one hand, by providing a suitable connecting means, for example of universal joint type, between the support plate for the shoes and the sliding return member which is axially disposed in the rotor Iand is subjected to` the action of Ia spring and, on the other hand, by positively driving this Iaxial return member through the medium of the roto-r. l

In a particular embodiment of this connectingy means, the latter is formed by a thin member comprising two lugs disposed in a recess in the support plate for the shoes and two lugs disposed in a recess disposed in the axial return member orthogonal to the other recess.

The positive driving in rotation of the return member may be ensured by la lug forming akey or by a sliding yconnecting between the return member and the end of the shaft journalled in the auxiliary bearing of the pump body, which has, for example, hat-faced portion and is slidably mounted in an aperture having a correspending shape formed in an axial extension o-f the return member.

Another improvement relates to the piston shoes. The spherical head of the piston is generally set in the shoe and the latter bears on the cam by a hat part. It is very advantageous to reduce the coefficient of friction ot the shoe on the cam so as to improve the eiciency land prolong the life of the pump.

For this pur-pose, it has already been proposed notably to mak-e the cam plate of graphite or to provide electrolytically a deposit or layer of metal on the shoe having a -goo-d coefficient of friction (cadmium, indium or silver, for example). But these solutions have disadvantages. In the first case, lthe graphite cannot support high mechanical stresses and the cam plate of lgraphite must incorporate a rigid reinforcement, for example of steel. The result is a rather space-consuming structure which is heterogeneous and might be rather fragile. In the second case, the electrolytic coatings on the shoe are thin and it is ditiicult to be sure of their adherence, and numerous diculties have arisen due to irregular deposits which ake oi.

According to the invention, the shoes are provided With an element comprising at least one at face and composed of a metal having a good coeticient of friction, for example silver, this elernent being disposed in the shoe in such manner that the flat face protrudes from the shoe and ensures that the shoe bears against the cam plate only through the medium of this at face. This element could be set in the shoe or could be simply maintained in position by the force exerted by the piston yon the cam.

In a particular embodiment ot said element, the latter is in the form oi a thin plate lodged in a shallow recess in the shoe.

In another embodiment, said element protrudes from the shoe not only on the side adjacent the cam but also on the side adjacent the head of the piston and they recess formed in the shoe is such that the spherical head of the piston is retained merely by the edges of the shoe and bears against the inner protruding face of said sliding element.

It can 'be seen that after Wear of the sliding plate or element of the invention, it is easily changed by dismantling the pump, whereas wear of the electrolytic deposits would require changing the entire shoe, that is, would require detaching the spherical end of the piston.

Further features and advantages of the invention will be apparent from the ensuing description, with reference to the accompanying drawings, of variable-flow drum piston pumps` incorporating the improvements of the invention.

In the drawings:

FIG. 1 is an axial sectional view of a pump having two outer bearings;

FIG. 2 is a view partily in section and partly in plan View taken along line II-I'I of FIG. 1;

FIG. 3 is a sectional View taken along line III- III of FIG. 1;

FIG. 4 is an axial sectional `'view of a modification of a detail of the pump shown in FIG. 1;

FIG. 5 is a partial axial sectional view of a modification of the pump shown in FIGS. l to 3 in which the balancing piston of the cam is replaced by a fixed abutment member rigid with the housing of the pump;

FIG. 6 Yis a sectional view taken along line VI'-VI of FIG. 5;

FIG. 7 is an axial sectional view of a pump having inner bearings and a central shaft;

PIG. '7a is a diagrammatic plan view `of :the pump of FIG. 73'showing the forces acting on the barrel and the resultant force thereof;

FIG. 7b lis a diagrammatic end view corresponding to FIG. 7a;

-FIG. 8 is an axial sectional view yof a detail of the Amounting of the piston shoes; and

FIG. 9 is lan axial sectionalview of a modification of the mounting .of -a .piston shoe.

In the embodiment shown in FIGS. 1 3, the pump com- -prises a-steel pump body or rotor 1 journalled in thehous- -ing 2 through the medium of 1a bearing 3 composed, for example, of graphite. The pump body, or rotor, is driven in rotation bya yshaft 4 through the medium of a gear 5 meshing with Aa ring gear 6 whose teeth are machined directly in the rotor 1.

lThe position of bearing 3 is determined by calculation as will -be'explained hereinafter with reference to `embodiment of FIG. vv7, in order that the resultantof the forces 'applied on rotor 1 falls Within the surface fof contact of the distribution member and the rotor 1. Said calculation shows here that said bearing 3l ought to be located -between the' vtransverse plane containing the pivot axis 20 of cam or swash plate 15 and vsaid distribution member, in the immediate vicinity of vsaid vtransverse plane.

In order to improve the centering of the rotor 1 in the `housing 2, `there is provided an additional bearing 7 car- -ried bythe housing and -in which is journalled the cy- -lindrical -extension'S of a shaft `9 which is fitted by a tapered portion 10 in the rotor '1 and held fast by a nut 11.

'The pump comprises pistons 12 -which slide in bores 13 formed'in ythe rotor, each of these bores being provided withla liner 14, for example composedof silver, to reduce `friction.

The pump delivery or discharge vflow is controlled by `a ftiltable cam or swash plate against the forward face of which the heads 16 of the pistons 12 bear through the medium of their shoes 17 and of a ybearing member, or plate, 18-

The cam 15 carries two ears 19, 19 provided with vapertures in which is journalled a pivot pin v20 carried by a support ,21 rigid with the housing. This pivot pin is adapted merely to maintain the cam 15 vin position and is only subjected to a small force owing to the provision -of'balancing means which will now be described.

' ,Providedin a bore 22 suitably disposed in the housing,

Yis a piston y23 which is constantly applied by its forward faceagainst the corresponding rear face 24 of the cam under the `effect of the delivery pressure of the pump prevailing in the chamber 22 at the rear of the piston. The forward face of the piston `and the corresponding part 24 of the cam have a part-cylindrical shape, the axis of the cylinder coinciding with the axis of the pivot pin 20 thereby permitting tilting of the cam.

By means of this arrangement, the cam 15 is constantly balanced by the action of the piston 23 whose position is precisely .determined so that its thrust balances substantially the resultant of the thrusts exerted on the cam by the pump pistons. The inclination or tilt of the cam is controlled by a small piston 25 actuated hydraulically and the return of the cam is ensured by the action of a piston 26 the rear of which is continuously subjected to Lthe delivery pressure.

In order to reduce friction, the support plate 1S of the shoes 17 of the pistons 16 is driven positively in rotation -by means of a .universal joint formed by a thin member 27 carrying upstanding lugs. Two of these lugs 28 are disposed in a slot 29 in the plate 18 and two other lugs are .disposed in a groove 3,0 orthogonal to the slot 29 and provided Vin a slide member 31 which is slidable in an axial bore 32 in the rotor and is biased toward the cam 15 by the effect of a return spring 33. The slide 31 is itselfpositively driven in rotation by the pump body owing to the provision Aof'keying on the shaft 9. This keying is formed, inthe presently-.described embodiment, by the yflat-faced end 35 of the shaft 9 which isengaged in the s waged portion 36 of the slide 31.

In the modification shown in FIG. .4. the slide 31 is ,driven directly -by the pump body through the medium .of a'pin rlv or the like forming a key.

lIn the'embodiment shown in FIGS.5 and 6, the bal- ,ancing of fthe cram 15 isxensured by the abutment of the latter against protruding portions or bosses 3S, 38' provided onrthe housing 2, the zone of contact between the l6.21m #15 and the portions 38, 38' being a part-cylindrical surface 39 the axis of the `cylinder coinciding with the pivot axis of the cam, namely, the axis of thepin 20. The resultant of the thrusts exerted on theV cam by the vpump pistonsy is therefore in this embodiment balanced Sby 4the reaction iof the housing on the cam.

In the embodiment shown 'in FIG. 7, the pump is mounted on ka central shaft. The elements corresponding .to those of zthe pumps shown in FIGS. 1-3 or 5 and 6 -carry the same reference characters.

:In this embodiment, the rotorl is ,mounted on a central shaft 40 rigidly fixed in the housing 2 and extend-ing through the pump. The rotor 1 is journalled on the shaft 40 through the medium of a main anti-friction or roller bearing 41 and a secondary antiafriction or roller 'hearing `42, the play in the latter being greater than that in the bearing 41. The rotorY 1 is driven by the shaft 4 through the medium of the gear 5 .meshed with the ring gear i directly machined in the rotor.

"The main bearing 41 isrsituated at the end of the ro- :tory adjacent the lcentrolcam 15 in a region which is determined by calculation in such manner that the resultant of the forcesapplied on the rotor 1 is directed toward 'the distribution surface 43 and falls within the surface of rcontact of this surface and the adjoining face of the rotor 1, in order that,'owing to this arrangement, the rotor 1 remains constantlyappliedpagainst the surface 43 during pump operation and the presence of the secondary bearing 42 in the vicinity of the face 43 also ensures correct application when-the pump is inoperative.

AThe above calculation is made in considering (see FIGS.' 7a and 7b) the rotor 1 and pistons 12, as a whole, submitted to the following forces:

(1) Resultaat Fp of the forces exerted by cam 15 on piston shoes ,17;V

(g2) Driving force (or couple of forces) FM;

(3) Hydraulic Aforce FH exerted on rotor'l by the uid kbottled up between said rotor and the distribution trans- -verse wall 43;

(4) Resilient force FR exerted by the resilient member (33, see FIG. 1), if any, to apply the piston heads 16 against cam 15;

(5) Reaction Rp of bearing 41, the moment of which is a function of the distance x between said bearing 41 and said transverse Wall 43;

(6) Reaction force RG of the transverse wall 43 on rotor 1.

It is the above reaction force RG which is the subject of the calculation and: RG=-e(Fp, FM, FH, FR, Rp).

For the calculation, the point of origin of the coordinates axes is chosen at the center of the distributor trans-r verse wall 43; the axes 0x, oy are in the plane of said wall 43, oy being directed towards the delivery port 45.

The magnitude and point of application of the diierent forces are determined by the following considerations:

(1) Resultant FP of the forces exerted by the cam 15 on the piston shoes 17 is perpendicular to said cam (providing there is no substantial friction); its point ,of application is at the center of gravity of the half-circle having a radius b equal to the boring radius of the piston bores, and its component parallel to the axis oz balances the force F generated by the delivery pressure of the pump applied to half of the number of pistons 12.

(2) Driving force FM has its point of application at the meshing point of driving gear 5 with thetoothed ring 6, its direction is defined by the pressure angle of the gear teeth, and its magnitude is determined by the fact that themoment, relative to axis oz, of its component parallel to x, balances the moment, rela-tive to the same axis, of FP.

When the rotor is driven through an axial drive, the driving shaft applies to the rotor a pure torque.

(3) The hydraulic force FH applied to the rotor is parallel to oz and its point of application is at the center of gravity of the half-circle having a radius c equal to the mean radius of the delivery and induction ports 45, 46, its magnitude is equal to the product of F and a factor which depends on the balancing coefficient of the pump.

(4) Force FR, in the case of an axial spring 33 (see FIG. 1) is applied at the origin of the coordinates axes and is parallel to oz.

(5) The reaction force Rp of the bea-ring 4l is perpendicular to oz and balances all components of the aforesaid forces which are perpendicular to oz.

(6) And the reaction force RG of the transverse wall 43 on rotor 1 is parallel to oz; its magnitude is equal to: FH-F-FR and its point of application in the plane of transverse wall 43 is determined by writing that the moments of said force RG relative to axes ox and oy are, respectively, equal to the sums of moments of aforesaid forces relative to the corresponding axes.

The coordinates of said point of application of RG being thus calculated, the conditions for said point to be inside the circle having the radius r of the distributor transverse member 43 give the limits between which is to be located the main bearing 41, to be sure that rotor 1 remains always correctly applied against said transverse wall 43 to provide a perfect working of the pump.

The secondary bearing 42 is in the sa-me transverse plane perpendicular to the shaft 40 as the ring gear 6 which is obviously most advantageous and only possible with a rotor mounted on a central shaft.

The line of meshing between the gears 5 and 6 is in the same plane as the axis of the induction passageways 44 and delivery passageways 45 and on the side of the axis of the rotor opposed to that of the delivery passageway 45. The application of the rotor against the distribution surface 43 is thereby still further improved.

The cam abuts, through the medium of a cylindrical boss formed thereon, against the parts 38 having corresponding shape of the housing 2 and can be tilted by a shaft which is integral therewith and disposed in a corresponding bore in the housing. The tilting of the cam 20 is controlled by a control lever 46 which is xed 5 on the end 47 of the shaft 20 and extends out of the housing through a suitable aperture.

In the embodiment shown in FIGS. 1 to 7, the spherical heads 16 of the pistons 12 are set into the shoes 17 and the latter bear on the cam 15 by their flat faces 47. In order to reduce friction, the shoe is covered on this face with a suitable electrolytic deposit or the cam is composed, for example, of graphite.

In the embodiment shown in FIG. 8, the shoe 17 cornprises a recess 48 in which is disposed a thin friction plate 49 which protrndes from the face 4/ of the shoe. Thus, the piston bears against the cam 15 solely through the medium of this plate 49 which is provided with an aperture 5t) for the passage of lubricating oil. This plate is composed of a metal having a good coefficient of friction, for example silver, and is easily changed when worn out.

In the modication shown in FIG. 9, the frictionplate is replaced by a substantially rrusto-conical element 51 Whose flat lface 52, protruding from the face 57 of the shoe 47, bears against the cam I5. The inner part 53 of the element 5I, disposed in an aperture of corresponding shape formed in the shoe, has a part-spherical concave shape and extends inwardly of the shoe. The recess in the shoe receiving the piston head has such shape that the piston head 16 is merely retained by the edges 54, it bearing solely against the concave part 53 of the element 51. Thus, friction both inside and outside the shoe only results in Wear of the element 53 which is easily changed.

Although specific embodiments of the invention have been described, many modifications and changes may be made therein without departing from the scope of the invention as defined in the appended claims. Thus, the pistons need not be parallel with one another and the shaft journalled in the lateral bearing could be mounted in the rotor by means other than a tapered extension held in place by a nut.

What I claim is:

1. In a pump of the drum piston type comprising a housing having a transverse wall and provided with an induction passageway and a delivery passageway opening on said transverse wall of said housing, a rotor mounted for rotation about an axis in said housing and having a lateral face in contact with a corresponding surface of said transverse Wall and bores opening on said lateral face, pistons disposed for reciprocation in said bores and having each a part-spherical head outside said rotor, a cam having a at face cooperating with said heads of said pistons for controlling the movement of said pistons in said rotor, a shoe mounted on each of said heads of said pistons and having a flat face resting against the said at face of said cam, a retaining plate for biasing said shoes against said cam, a spring biased member axially and slidingly mounted in said rotor, said spring biased member and said plate providing contacting surfaces between the spring biased member and the plate, said contacting surfaces providing grooves and projections fitting in said grooves for positively driving the plate via the spring biased member.

2. In a pump of the drum piston type co-mprising a housing having a transverse wall and provided with an induction passageway and a delivery passageway opening on said transverse wall of said housing, a rotor mounted for rotation about an axis in said housing and having a lateral face in contact with a corresponding surface of said transverse Wall and bores opening on said lateral face, pistons disposed for reciprocation in said bores and having each a part-spherical head outside said rotor, a cam having a flat face cooperating with said heads of said pistons for controlling the movement of said pistons in said rotor, a shoe mounted on each of said heads of said pistons and having a at fa-ce resting against said dat face of said cam, a retaining plate for applying said shoe against said cam and having a hemispherical portion, a spring biased member axially and slidingly mounted in said rotor but keyed in rotation with said rotor and having a hemispherical portion fitting with said hemispherical portion of said retaining plate'for urging said plate landsaid shoes towards said cam, grooves on one ,of said corresponding hemispherical portions Vof said retaining plate and said Vspring biased members, and proiections on the other of said hemispherical portions engaging vvith and cooperating with said grooves.

3. I n a pump ofv the drum piston type comprising a housing having atransverse Wall and provided with an induction passageway and adelivery passageway opening on said transverse Wall of said housing for circulation ofthe fluid to be circulated by said pump,` a rotor mounted Ifor rotation about an axis in said housing and having a lateral face incontact With a corresponding surface of -said transverse Wall exerting on said rotor a reaction force substantially perpendicular ,to said lateral face and bores opening on saidlateral face, pistons disposed for reciprocation in said bores and having each a head outside said rotor, a cam cooperating with said heads for controlling the'movement of rsaid pistons in said rotor comprising a support mounted for rocking movement about an axis exltending at right angles to the axis of rotation of ,Said rotor and exerting'on said piston heads forces ywhich have va resultant perpendicular to saidicam, -resilient means urging said pistons against ysaid cam thereby exerting a force .on said rotor, a -toothed ring 'directlyv machined in the lateral face .of said rotor,- and Aa 4driving shaft having lits axis parallel to .the axis of rotation of said rotor, a gear carried by said driving shaftand meshing with said ltoothed ring for rotating said rotor and .exerting on said rotor ya driving force, a .main bearing for supporting said rotor in Vsaid Vhousing and `exertingon said rotor a bearing reaction force substantially perpendicular to said Y.axis of ,said `rotor and forming with said resultant force .exerted by said cam on said piston heads, said-,hydraulic force, said driving force, said force exerted byfsaid resilient meansand said reaction -force'exerted by said transverse ,wall on said rotor a system of forces having a zero resultant, said main ,bearing being located in a plane between the Vtransverse plane containing Vthe Aaxis oirocking movement of said cam and saidtransversewalrlat .ai'disyA tance from said transverse Wall such yas to have said reac-l tion force exerted lby said transverse vwall Non' said vrotor fall inside said corresponding surface of Asaid1transvelrse Wall and be directed towards said rotor.

4. In la pump as in claim 3, further comprising aV secondary bearing located substantially in the plane containf ing said toothed ring and supporting said rotor with `a play exceeding the play of said main bearing.

5. VIn a pump asin claim 3, wherein said ldelivery passageway is located in the axial plane containing theline of mesh between said toothed ring and said gear on the side of the axis of the otor opposed to that y,of said line ofmesh.

References Cited in the tile `of this patent UNHED .SATsS PATENTS Martin June 6, A192?.

1,710,567 Carey Q pr. 23, 1929 1,996,889 Thomas V Apr. 9,4193-5 2,063,464 Schindler Dec. 8,1936 2,284,146 Herman4 A -Mayi2`6', 1942 2,480,069 Wright Ang. 23, .1949 2,484,337 Ferris v.` l p ..o'ct,f11, 11949 2,502,546 Adams s Apr. 4, 1950 2,543,624 Gabriel 1....'.5112615. 27, 1951 2,549,711 Ruben Apr. 17,1951 `2,642,809 Born et a-l June 23,1953 2,699,123l Bonnette et al. Jans-11', 1955 2,716,944 Ferris d .'Sept. 6, `11955 2,733,666 Poulos Fe'b. 7, 1956 2,776,629 .Keel j Jan; 8', 1957 V2,800,082 Aspelin Ju1y123, '1957 v2,880,042 Budzich ...r. j Man '311, 1959 2,895,426 -orshans-ky j' '11`y p21; V19'5'9 FOREIGN PATENTS I 119,044 Switzerland 'Mar.11, y1927 

1. IN A PUMP OF THE DRUM PISTON TYPE COMPRISING A HOUSING HAVING A TRANSVERSE WALL AND PROVIDED WITH AN INDUCTION PASSAGEWAY AND A DELIVERY PASSAGEWAY OPENING ON SAID TRANSVERSE WALL OF SAID HOUSING, A ROTOR MOUNTED FOR ROTATION ABOUT AN AXIS IN SAID HOUSING AND HAVING A LATERAL FACE IN CONTACT WITH A CORRESPONDING SURFACE OF SAID TRANSVERSE WALL AND BORES OPENING ON SAID LATERAL FACE, PISTONS DISPOSED FOR RECIPROCATION IN SAID BORES AND HAVING EACH A PART-SPHERICAL HEAD OUTSIDE SAID ROTOR, A CAM HAVING A FLAT FACE COOPERATING WITH SAID HEADS OF SAID PISTONS FOR CONTROLLING THE MOVEMENT OF SAID PISTONS IN SAID ROTOR, A SHOE MOUNTED ON EACH OF SAID HEADS OF SAID PISTONS AND HAVING A FLAT FACE RESTING AGAINST THE SAID FLAT FACE OF SAID CAM, A RETAINING PLATE FOR BIASING SAID SHOES AGAINST SAID CAM, A SPRING BIASED MEMBER AXIALLY AND SLIDINGLY MOUNTED IN SAID ROTOR, SAID SPRING BIASED MEMBER AND SAID PLATE PROVIDING CONTACTING SURFACES BETWEEN THE SPRING BIASED MEMBER AND THE PLATE, SAID CONTACTING SURFACES PROVIDING GROOVES AND PROJECTIONS FITTING IN SAID GROOVES FOR POSITIVELY DRIVING THE PLATE VIA THE SPRING BIASED MEMBER. 